Sneak Peek: Tears and Heartache on Polygamy Show Sister Wives

Before their legal troubles, the Browns had to deal with different kind of drama at home.

The stars of TLC's Sister Wives, who are under police investigation in Utah for a possible charge of felony bigamy, reveal they clashed over a lip-locking incident.

"Kody sealed the engagement [with his fourth wife Robyn] with a kiss and I freaked," Kody Brown's third wife, Christine, says in a preview of Sunday's new back-to-back episodes (10 p.m. ET). "We didn't kiss until over the altar because I didn't feel right about kissing a married man."

Robyn, likewise, was surprised by the kiss and says she was saddened it caused so much pain.

"I found out that Christine was upset," she says, breaking down in tears. "I remember being really upset cause I knew I'd hurt you. I knew it'd be complicated but I didn’t know it would break my heart as well."

TLC will air an encore of the Sister Wives series premiere on Wednesday (7 p.m. ET).